The invention relates to a testing apparatus which automatically handles a plurality of samples
In the testing of the durability of rubber compounds, one test that is used is a dynamic flexing test. In the dynamic flexing test, the rubber being tested is formed into a thin sample and two ends of the sample are anchored in opposing sample holders. The sample holders are fixed into an apparatus which is capable of stretching the sample at 10 cycles per second or more. Prior to flexing the sample, a small cut is placed in the edge of the sample to initiate cracking of the rubber, and the fracture resistance of the rubber comprising the sample is measured by the propagation rate of a crack resulting from the dynamic flexing.
The length of the crack, and the path of the crack provide information to the engineer which can be used to make predictions as to the performance of the rubber when used as a component of an elastomeric product.
In the prior art, measurements were made manually and a written description of the cut path was provided. In some embodiments of the test, pictures were taken of the sample after completion of the flex testing.
In variations of the test, the rubber sample may be subjected to aging, i.e. subjected to oxidizing or reducing atmosphere and heated, to get additional data on the aging properties of the rubber sample.
The testing of individual samples, or a small number of samples is laborious and time-consuming. There is a need in the art for an apparatus and method whereby a large number of samples can be tested simultaneously and the results can be determined substantially automatically.
The invention relates to an apparatus for automatically testing multiple samples comprising a carousel having a plurality of stations for holding samples to be tested. Sample holding means associated with the carousel are adapted to retain samples during static or dynamic testing of the samples and to release the samples when measurements are made.
In the illustrated embodiment, a vacuum device associated with the carousel is used to remove a sample from the sample holding means, and a measuring device associated with the carousel is used for evaluating a sample when a sample is withdrawn from the sample holding means by the vacuum device.
In the illustrated embodiment, the sample holding means and vacuum device are contained within an environmental chamber and the measuring device is an imaging device outside the environmental chamber.
The carousel has an upper part and a lower part and the sample holding means has a first portion associated with the upper part of the carousel and a second portion associated with the lower part of the carousel. The lower part and upper part of the carousel are moveable relative to one another, i.e. the upper portion and the lower portion of the carousel are actuated to move toward and away from each other while sample holding means in the upper portion and lower portion remain aligned.
The upper portion and the lower portion of the carousel are mounted on a spindle, and actuating means is provided for advancing the carousel in increments corresponding to sample holding means in the carousel. In the illustrated embodiment, the lower portion and upper portion of the carousel are actuated ten times per second to provide dynamic flexing of rubber samples.
The environmental chamber has means for controlling atmosphere and temperature.
In the illustrated embodiment of the invention, the measuring means is a digital imaging device.
A method for automating the testing of a sample using the apparatus of the invention is also provided.